Portable desk



FIG. 1 is an interior perspective view of a portable desk showing my new design in an open position;

FIG. 2 is an exterior perspective view thereof;

FIG. 3 is a top plan view of FIG. 5;

FIG. 4 is a bottom plan view of FIG. 5 with the top member folded down over the center member and the end straps attached to the bottom; and

FIG. 5 is a right side elevational view of FIG. 1. 

The ornamental design for a portable desk, as shown and described. 